Cosmetic changes per EH patch review feedback.

llvm-svn: 49096
diff --git a/llvm/lib/CodeGen/DwarfWriter.cpp b/llvm/lib/CodeGen/DwarfWriter.cpp
index 0fa956e..010dfa0 100644
--- a/llvm/lib/CodeGen/DwarfWriter.cpp
+++ b/llvm/lib/CodeGen/DwarfWriter.cpp
@@ -3415,7 +3415,7 @@
   void BeginFunction(MachineFunction *MF) {
     this->MF = MF;
     shouldEmitTable = shouldEmitMoves = false;
-    if (TAI->doesSupportExceptionHandling()) {
+    if (MMI && TAI->doesSupportExceptionHandling()) {
 
       // Map all labels and get rid of any dead landing pads.
       MMI->TidyLandingPads();